1. Field of the Invention
The invention relates to clutches and more particularly to clutches which are operated automatically by centrifugal force at a predetermined speed of rotation so as to connect a driving member to a driven member or load. More particularly, the invention relates to a centrifugal clutch construction in which the driving and driven members are coupled together instantaneously upon the driving member reaching a predetermined speed, which engagement speed is considerably higher than the disengagement speed of the coupled members.
2. Description of the Prior Art
There are numerous types and arrangements of centrifugal clutch constructions in which one or more clutch shoes are retained in retracted position until sufficient centrifugal forces act on the shoes to overcome a retaining spring whereupon the clutch shoes move outwardly and engage a stationary clutch drum. Such clutch constructions experience excessive wear of the clutch shoes linings since the coupling engagement is gradual as the driving member comes up to engagement speed resulting in undesirable slippage and heating between the shoe lining material and driven member.
Various centrifugal clutch constructions have been developed to provide a more sudden or instantaneous engagement of the clutch shoes with the clutch drum to eliminate such undesirable wear and heating. Many of these delayed action clutch constructions use spring means to retain the clutch shoes in retracted position and to actuate the rapid engagement. Examples of such clutch constructions are shown in U.S. Pat. Nos. 1,737,825, 2,000,713, 3,367,463, and 3,752,285.
Other clutch constructions use other delay engagement means, such as a fluid dashpot as shown in U.S. Pat. No. 3,850,276, while still other clutch constructions use spring means to achieve an instantaneous disengagement of the clutch shoes from the driven member as opposed to instantaneous engagement. Examples of these clutch constructions are shown in U.S. Pat. Nos. 2,534,133, 2,755,902, and 3,367,463.
The use of springs or spring biased members as one of the principle components to achieve this instantaneous engagement feature presents problems in that a spring's characteristics are affected by change in ambient temperature, age, wear, etc., and the springs are subject to breakage and maintenance problems.
There is no known clutch construction of which I am aware which provides an instantaneously engageable clutch construction which engages at a considerably higher speed than its disengagement speed without the use of springs or fluid dashpot means as a primary retention means delaying engagement; and in which a high engagement speed is attained with a high mass clutch to produce a high coupling torque in comparison with known clutch constructions requiring a low mass clutch to achieve such a high speed engagement level with the resulting lower coupling torque.